System and Methods of Using Image-Guidance for Providing an Access to a Cochlear of a Living Subject

ABSTRACT

A system and methods for providing an access to a cochlea of a living subject. In one embodiment of the present invention, a method comprises the steps of operating a surgical instrument towards a region of interest of the living subject for opening an access to the cochlea of the living subject from the lateral edge of the skull of the living subject to the cochlea of the living subject, and intra-operatively monitoring at least a part of the surgical instrument so that the surgical instrument is operated substantially along a predetermined path.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit, pursuant to 35 U.S.C. §119(e), ofU.S. provisional patent application Ser. No. 60/676,436, filed Apr. 29,2005, entitled “System and Methods of Using Image-Guidance for Placementof Cochlear Stimulator Devices, Drug Carrier Devices, or the Like,” byRobert F. Labadie, and J. Michael Fitzpatrick, which is incorporatedherein by reference in its entirety.

This application is related to a copending U.S. patent applicationentitled “System And Method For Surgical Instrument Disablement ViaImage-Guided Position Feedback”, U.S. patent application Ser. No.11/079,898, filed 14 Mar. 2005 with the same applicants and assignee asthe present invention. The disclosure of the above identified copendingapplications is incorporated herein by reference.

Some references, which may include patents, patent applications andvarious publications, are cited and discussed in the description of thisinvention. The citation and/or discussion of such references is providedmerely to clarify the description of the present invention and is not anadmission that any such reference is “prior art” to the inventiondescribed herein. All references cited and discussed in thisspecification are incorporated herein by reference in their entiretiesand to the same extent as if each reference was individuallyincorporated by reference. In terms of notation, hereinafter, “[n]”represents the nth reference cited in the reference list. For example,[10] represents the 10th reference cited in the reference list, namely,Labadie R F, Fenlon M, Devikalp H, et al. Image-guided otologic surgery.Computer Assisted Radiology and Congress and Exhibition (eds: Lemke H U,Vannier M W, Inamura K, Farman A G, Doi K, Reiber J H C) pp. 627-32.Elsevier Science, Amsterdam, The Netherlands, 2003.

STATEMENT OF FEDERALLY-SPONSORED RESEARCH

The present invention was made with Government support under a contractR21 EB02886-01 awarded by the National Institute of Biomedical Imagingand Bioengineering. The United States Government may have certain rightsto this invention pursuant to this grant.

FIELD OF THE INVENTION

The present invention generally relates to image-guided surgery, andmore particularly to a system and methods of using image-guidance forproviding an access to a cochlea of a living subject for performing amedical procedure.

BACKGROUND OF THE INVENTION

Image-guided surgery (hereinafter “IGS”) technology has been clinicallyavailable since the mid-1980's [1]. Analogous to a global positioningsystem (hereinafter “GPS”), IGS facilitates intra-operative surgicalnavigation by linking pre-operative radiographs to intra-operativeanatomy. Central to the IGS process is registration—the linking of theradiographic images to the patient. To achieve high accuracy theregistration is based on fiducial markers are identified in both theradiographs and on the patient. A mathematical transformation matrix iscreated to optimize the alignment of the fiducial markers. This sametransformation matrix is then applied to all information in theradiograph allowing an overlay of the radiograph onto the patient'sphysical anatomy. This information is typically presented to the surgeonvia a video monitor; a pointer placed within the surgical field islinked to a cursor on the monitor to show the corresponding radiographicposition in axial, saggital, and coronal sections.

IGS is widely used in neurosurgery where the gold standard fiducial is arigidly affixed N-frame. Screwed directly into the cranium, the N-frameis secured before imaging studies are obtained and remains in placethroughout surgical intervention. Such stereotactic frames are invasiveand cumbersome. However, given a life-threatening disease such as amalignant brain tumor, they are tolerated by patients. Neurosurgicalstudies have shown that IGS decreases operative time [2] and allows morecomplete resection of pathologic tissue while minimizing collateraldamage [3].

As applied to otology and neurotology, IGS has found limited use.Isolated case reports describe their use in patients with unusualanatomy. Utilizing a modified neurosurgical unit, Sargent and Bucholzreported on IGS for middle cranial fossa approaches [4]. Raine et al.utilized an IGS system for split-electrode cochlear implant placement ina patient with cochlear ossification [5]. In perhaps the most widespreaduse, Caversaccio et al. reported their series of aural atresia repairusing IGS guidance [6].

The reasons that IGS technology has found limited clinical applicationin otology/neurotology remain unclear. Hypothetically, its use has beenstalled by the need for non-invasive, yet accurate, fiducial systems. Toachieve submillimetric IGS accuracy—necessary to prevent damage to vitalstructures within the temporal bone—bone-affixed fiducial systems havebeen necessary. At present, less invasive fiducial systems are lessaccurate; skin-affixed markers achieve accuracies in the range of 1.5 mmand laser skin contouring achieves accuracies in the range of 2.5 mm [7,8].

Therefore, a heretofore unaddressed need still exists in the art toaddress the aforementioned deficiencies and inadequacies.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a method for providingan access to the cochlea of a living subject, where the access to thecochlea of the living subject is a single passage from the lateral edgeof the skull to the cochlea. In one embodiment, the method includes thesteps of non-invasively placing a plurality of fiducial markerssurrounding the cochlea of the living subject, and pre-operativelyacquiring an image volume from the cochlea of the living subject, wherethe pre-operatively acquired image volume contains the image of theplurality of fiducial markers. In one embodiment, the non-invasivelyplacing step comprises the step of mounting a locking dental acrylicresin splint (LADS) with an attached fiducial frame onto a maxilla ofthe living subject, where the fiducial frame is adapted for receivingthe plurality of fiducial markers. The pre-operatively acquiring step isperformed with an imaging acquisition device.

The method further includes the steps of identifying a centroid of eachfiducial marker from the pre-operatively acquired image volume,pre-operatively measuring a location of each fiducial marker in ananatomic space of the cochlea of the living subject, registering theidentified centroid of each fiducial marker in the pre-operativelyacquired image volume to the pre-operatively measured location of thecorresponding fiducial marker in the anatomic space so as to determine aregistration transformation.

Furthermore, the method includes the steps of operating a surgicalinstrument along a predetermined path to open an access to the cochleaof the living subject, the surgical instrument having a distal endportion, tracking the distal end portion of the surgical instrumentthrough a first optical emitter attached to the optical instrument andan optical tracker adapted for receiving optical signal from the firstoptical emitter, and intra-operatively guiding the surgical instrumentthrough visualizing a location of the distal end portion of the surgicalinstrument in the pre-operatively acquired image volume.

The pre-operatively measuring step is performed with a localizing probe,where the localizing probe is coupled with the first optical emitter.

The operating step, in one embodiment, is performed by a human being. Inanother embodiment, the operating step is performed at least in part bya man-made device such as a robot.

In one embodiment, the intra-operatively guiding step comprises thesteps of intra-operatively monitoring the location of the distal endportion of the surgical instrument in the anatomic space of the cochleaof the living subject, and mapping the intra-operatively monitoredlocation of the distal end portion of the surgical instrument in theanatomic space onto a corresponding location in the pre-operativelyacquired image volume by an inverse of the registration transformation,where the intra-operatively monitoring step is performed with the firstoptical emitter and the optical tracker.

Moreover, the method includes the step of intra-operatively tracking atleast a portion of the skull of the living subject through a secondoptical emitter attached to LADS and the optical tracker adapted forreceiving optical signal from the second optical emitter.

Additionally, the method includes the step of disabling the surgicalinstrument when the surgical instrument departs from the predeterminedpath.

The method may also include the step of performing a therapeutic medicalprocedure or a diagnosis medical procedure through the access to thecochlea of the living subject. The therapeutic medical procedurecomprises a medical procedure for placement of one of a cochlearimplant, a drug delivery system, a carrier device, a medical detectingsystem, a medical treatment system, and any combination of them. Thediagnosis medical procedure comprises a medical procedure for using amedical device to detect and collect information related to the livingsubject.

In another aspect, the present invention relates to a system forproviding an access to the cochlea of a living subject. In oneembodiment, the system has means for non-invasively placing a pluralityof fiducial markers surrounding the cochlea of the living subject. Inone embodiment, the placing means comprises a locking dental acrylicresin splint (LADS) mountable to a maxilla of the living subject,wherein the LADS includes a central portion with an extension at apredetermined position, and two lateral portions attached to the centralportion, and a fiducial frame attachable to the LADS by the extensionfor receiving the plurality of fiducial markers.

The system also has an imaging acquisition device for pre-operativelyacquiring an image volume from the cochlea of the living subject, thepre-operatively acquired image volume containing the image of theplurality of fiducial markers. In one embodiment, the imagingacquisition device comprises a CT scanning device.

The system further has a surgical instrument having a distal end portionfor opening an access to the cochlea of the living subject. In oneembodiment, the surgical instrument comprises a drill, and the distalend portion of the surgical instrument comprises the tip of the drill.In another embodiment, the surgical instrument comprises a surgicalscalpel, and the distal end portion of the surgical instrument comprisesthe cutting portion of the surgical scalpel.

Furthermore, the system has an infrared tracking system forpre-operatively measuring a location of each fiducial marker andintra-operatively monitoring a location of the distal end portion of thesurgical instrument in the anatomic space of the cochlea of the livingsubject. The infrared tracking system comprises a first optical emitterattachable to the surgical instrument, and a second optical emitterattachable to the LADS, and an optical tracker adapted for receivingoptical signals from the first optical emitter and the second opticalemitter, respectively. In one embodiment, each of the first and secondoptical emitters comprises an infrared emitter.

Moreover, the system has a controller for receiving and processing datarelated to the pre-operatively acquired image volume, thepre-operatively measured location of each fiducial marker and theintra-operatively monitored location of the distal end portion of thesurgical instrument so as to guide the surgical instrument along apredetermined path to open an access to the cochlea of the livingsubject. The controller, in one embodiment, is programmed to perform thesteps of identifying a centroid of each fiducial marker in thepre-operatively acquired image volume, registering the identifiedcentroid of each fiducial marker in the pre-operatively acquired imagevolume to the pre-operatively measured location of the correspondingfiducial marker in the anatomic space so as to determine a registrationtransformation, and mapping the intra-operatively monitored location ofthe distal end portion of the surgical instrument in the anatomic spaceonto a corresponding location in the pre-operatively acquired imagevolume by an inverse of the registration transformation, therebyintra-operatively displaying the location of the distal end portion ofthe surgical instrument. Furthermore, the controller is programmed toperform the step of disabling the surgical instrument when the surgicalinstrument departs from the predetermined path.

Additionally, the system has an image display device in communicationwith the controller for displaying the location of the distal endportion of the surgical instrument. The image display device in oneembodiment comprises a monitor.

In yet another aspect, the present invention relates to a method forproviding an access to the cochlea of a living subject. The access tothe cochlea of the living subject is a single passage from the lateraledge of the skull to the cochlea. The method in one embodiment comprisesthe steps of providing a platform and a surgical instrument guide,pre-operatively determining a location for positioning the platformproximate to the cochlea of a living subject, positioning the platformproximate to the cochlea of a living subject to the pre-operativelydetermined location, operating a surgical instrument towards a region ofinterest of the living subject, where the surgical instrument has adistal end portion in operation reaching the region of interest foropening an access to the cochlea of the living subject,intra-operatively guiding the surgical instrument through the surgicalinstrument guide, and intra-operatively monitoring at least a locationof the distal end portion of the surgical instrument so that thesurgical instrument is operated substantially along a predeterminedpath.

The method further comprises the step of performing a therapeuticmedical procedure or a diagnosis medical procedure through the access tothe cochlea of the living subject. The therapeutic medical procedurecomprises a medical procedure for placement of one of a cochlearimplant, a drug delivery system, a carrier device, a medical detectingsystem, a medical treatment system, and any combination of them. Thediagnosis medical procedure comprises a medical procedure for using amedical device to detect and collect information related to the livingsubject.

The method also comprises the step of disabling the surgical instrumentwhen the surgical instrument departs from the predetermined path.

In one embodiment, the platform comprises a fiducial frame with at leastone fiducial marker, where the fiducial frame comprises a customizedfiducial frame. The operating step is performed by a human being, or atleast in part by a man-made device such as a robot. The surgical guideincludes an infrared tracking system. The pre-operatively determiningstep is performed with a registration procedure. The intra-operativelymonitoring step is performed with an image-guided procedure.

In a further aspect, the present invention relates to a system forproviding an access to the cochlea of a living subject. The access tothe cochlea of the living subject is a single passage from the lateraledge of the skull to the cochlea. In one embodiment, the system has aplatform, means for pre-operatively determining a location forpositioning the platform proximate to the cochlea of the living subject,means for positioning the platform proximate to the cochlea of theliving subject to the pre-operatively determined location, a surgicalinstrument guide for guiding a surgical instrument towards a region ofinterest of the living subject, wherein the surgical instrument has adistal end portion in operation reaching the region of interest first,for opening an access to the cochlea of the living subject, and meansfor intra-operatively monitoring at least a location of the distal endportion of the surgical instrument so that the surgical instrument isoperated substantially along a predetermined path.

The system further has means for performing a medical procedure throughthe access. In one embodiment, the means for performing a medicalprocedure comprises a cochlea implant, a drug delivery system, a carrierdevice, a medical detecting system, a medical treatment system, and anycombination of them.

The platform comprises a fiducial frame with at least one fiducialmarker, where the fiducial frame comprises a customized fiducial frame.

The surgical instrument guide comprises an infrared tracking system. Inone embodiment, the surgical instrument comprises a drill, and thedistal end portion of the surgical instrument comprises the tip of thedrill. In another embodiment, the surgical instrument comprises asurgical scalpel, and the distal end portion of the surgical instrumentcomprises the cutting portion of the surgical scalpel.

The means for pre-operatively determining a location comprises acontroller and/or software stored on a computer readable medium forcausing the controller to perform at least a registration procedure.

The intra-operatively monitoring means comprises a controller and/orsoftware stored on a computer readable medium for causing the controllerto perform at least an image-guided procedure. The intra-operativelymonitoring means further comprises an image displaying device incommunication with the controller.

The system further has means for disabling the surgical instrument whenthe surgical instrument departs from the predetermined path.

In yet a further aspect, the present invention relates to a method forproviding an access to the cochlea of a living subject. In oneembodiment, the method includes the steps of operating a surgicalinstrument towards a region of interest of the living subject foropening an access to the cochlea of the living subject from the lateraledge of the skull of the living subject to the cochlea of the livingsubject, and intra-operatively monitoring at least a part of thesurgical instrument so that the surgical instrument is operatedsubstantially along a predetermined path.

The method further includes the step of disabling the surgicalinstrument when the surgical instrument departs from the predeterminedpath.

The method also includes the step of intra-operatively and independentlymonitoring a position of the skull of the living subject.

These and other aspects of the present invention will become apparentfrom the following description of the preferred embodiment taken inconjunction with the following drawings, although variations andmodifications therein may be affected without departing from the spiritand scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows (A) an EarMark™ fiducial frame system worn duringpre-operative radiographic imaging, and (B) an infrared emitter wornduring surgery. In panel (A), fiducial markers placed on the horizontalbar and vertical bar are arranged to surround the surgical field ofinterest—the temporal bone. The fiducial frame is affixed to themaxillary dentition via a customized mouthguard—a locking dental acrylicresin splint (hereinafter “LADS”). In panel (B), the infrared emitter isattached to the LADS as a rigid extension of the EarMark™ fiducial framesystem, which allows unimpeded access to the temporal bone duringsurgery.

FIG. 2 shows schematically an image-guided otologic surgery systemaccording to one embodiment of the present invention: (A) the systemincluding an infrared tracking system, a surgical tool, a computer, anda video monitor, (B) a photograph of a skull with the surgical toolcoupled with an infrared emitter, and (C) a photograph of the surgicaltool coupled with the infrared emitter.

FIG. 3 shows a surgical navigation with IGS according to one embodimentof the present invention: (A) a transverse, (B) a coronal and (C) asagittal view of the surgical field of interest visualized in themonitor, where the distal end portion of the surgical tool is localizedon the pre-operatively obtained CT scanned image, and (D) a photographof the skull with the surgical tool coupled with an infrared emitter.

FIG. 4 shows a magnified oblique image with the drill path shown as awide line. This path can be seen approaching the basal turn of thecochlea. The stylomastoid foramen can be seen inferior to this.

FIG. 5 shows photographs of surgical dissection of Skull No. 1 accordingto one embodiment of the present invention: (A) and (B) showing the pathof the image-guided drill as it enters the middle ear via the facialrecess, and (C) and (D) showing the same skull after traditionalmasotidecotmy preserving the path of the drill. In these panels, thevertical wire is located in the stylomastoid foramen and the horizontalwire passes through the drill path.

FIG. 6 shows photographs of surgical dissection of Skull No. 2 accordingto one embodiment of the present invention: (A) showing the path of theimage-guided drill as it enters the middle ear via the facial recess. Awire has been feed through this tunnel, and (B) showing thepost-mastoidectomy drilling with exposure of the semicircular canals(arched wire), sigmoid sinus, and facial canal (vertical wire). Thedrill path does not violate any of these structures.

FIG. 7 shows a flowchart for providing an access to the cochlea of aliving subject for performing a medical procedure according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is more particularly described in the followingexamples that are intended as illustrative only since numerousmodifications and variations therein will be apparent to those skilledin the art. Various embodiments of the invention are now described indetail. Referring to the drawings, like numbers indicate like partsthroughout the views. As used in the description herein and throughoutthe claims that follow, the meaning of “a,” “an,” and “the” includesplural reference unless the context clearly dictates otherwise. Also, asused in the description herein and throughout the claims that follow,the meaning of “in” includes “in” and “on” unless the context clearlydictates otherwise. Moreover, titles or subtitles may be used in thespecification for the convenience of a reader, which has no influence onthe scope of the invention. Additionally, some terms used in thisspecification are more specifically defined below.

Definitions

The terms used in this specification generally have their ordinarymeanings in the art, within the context of the invention, and in thespecific context where each term is used.

Certain terms that are used to describe the invention are discussedbelow, or elsewhere in the specification, to provide additional guidanceto the practitioner in describing the apparatus and methods of theinvention and how to make and use them. For convenience, certain termsmay be highlighted, for example using italics and/or quotation marks.The use of highlighting has no influence on the scope and meaning of aterm; the scope and meaning of a term is the same, in the same context,whether or not it is highlighted. It will be appreciated that the samething can be said in more than one way. Consequently, alternativelanguage and synonyms may be used for any one or more of the termsdiscussed herein, nor is any special significance to be placed uponwhether or not a term is elaborated or discussed herein. Synonyms forcertain terms are provided. A recital of one or more synonyms does notexclude the use of other synonyms. The use of examples anywhere in thisspecification, including examples of any terms discussed herein, isillustrative only, and in no way limits the scope and meaning of theinvention or of any exemplified term. Likewise, the invention is notlimited to various embodiments given in this specification. Furthermore,subtitles may be used to help a reader of the specification to readthrough the specification, which the usage of subtitles, however, has noinfluence on the scope of the invention.

As used herein, “around”, “about” or “approximately” shall generallymean within 20 percent, preferably within 10 percent, and morepreferably within 5 percent of a given value or range. Numericalquantities given herein are approximate, meaning that the term “around”,“about” or “approximately” can be inferred if not expressly stated.

As used herein, the term “living subject” refers to a human being suchas a patient, or an animal such as a lab testing rat, gerbil, monkey orthe like.

The term “cochlea,” as used herein, refers to a spiral-shaped cavity ofan inner ear that resembles a snail-like shell and contains nerveendings essential for hearing. The snail-like structure is buried deeplywithin the temporal bone and located on either sides of the skull. Acochlea includes three fluid-filled chambers: scala tympani and scalavestibuli (both of which contain perilymph), and scala media (whichcontains endolymph).

The term “cochlear implant”, as used herein, refers to a device that isplaced into scala tympani of a cochlea to provide sound perception fordeaf or hearing impaired individuals.

Overview of the Invention

The widespread use of IGS in otologic surgery has been limited by theneed for a system that achieves the necessary level of accuracy with aneasy-to-use, non-invasive fiducial marker system. The inventorsaccording to the present invention have developed such a system andrelated methods/procedures, where submillimeteric accuracy is achieved.With this system, image-guided otologic surgery permits accurate accessto the middle ear via the facial recess using a single drill hole fromthe lateral aspect of the mastoid cortex so as to perform a medicalprocedure. The medical procedure includes a therapeutic medicalprocedure or a diagnosis medical procedure. The therapeutic medicalprocedure may be corresponding to a medical procedure for placement ofone of a cochlear implant, a drug delivery system, a carrier device, amedical detecting system, a medical treatment system, and anycombination of them. The diagnosis medical procedure may comprise amedical procedure for using a medical device to detect and collectinformation related to a patient.

In accordance with the purposes of this invention, as embodied andbroadly described herein, this invention, in one aspect, relates to amethod for providing an access to the cochlea of a living subject,comprising the steps of operating a surgical instrument towards a regionof interest of the living subject for opening an access to the cochleaof the living subject from the lateral edge of the skull of the livingsubject to the cochlea of the living subject and intra-operativelymonitoring at least a part of the surgical instrument so that thesurgical instrument is operated substantially along a predeterminedpath. Accordingly, the image-guided otologic surgery performed based onthe present invention provides an access, in the form of a singlepassage, to the middle ear via the facial recess in aminimally-invasive, percutaneous fashion.

Another aspect of the present invention provides a system of animage-guided otologic surgery for providing an access to the cochlea ofa living subject to perform a medical procedure. Referring to FIGS. 1and 2, the system 100 includes means for non-invasively placing aplurality of fiducial markers surrounding the cochlea of the patient. Asshown in FIG. 1A, the placing means 110 has an LADS 112 mounted to amaxilla of the living subject and a fiducial frame 114 attached to theLADS 112. The LADS 112 resembles an athletic mouthguard but comprisesthree pieces instead of one: a central piece with an extension at apredetermined position, which engages the biting surfaces of the teethof the patient, as well as right and left buccal pieces, which engagethe lateral surfaces of the teeth of the patient. The three pieces areattached together with screws which lock the components around thecrowns of the teeth of the living subject thereby fixing the mouthpiecereliably in place while allowing it to be removed and replaced in thesame position and orientation. The fiducial frame 114 is a lightweightyet rigid frame which extends to surround the external ears of theliving subject for placing the plurality of fiducial markers 115 inclose proximity to the temporal bone. As shown in FIG. 1A, the fiducialframe 114 is corresponding to an EarMark™ system developed by theinventors [9-11]. The EarMark™ system 114 is secured to the skull 119 ofthe living subject by mounting the LADS 112 onto the maxilla of thepatient. Rigid fixation of the fiducial markers 115 to the EarMark™system 114 is advantageous because it avoids drilling into the skull119. In this embodiment, twelve fiducial markers 115, such as Acustar®of Z-Kat, Inc., Hollywood, Fla., are received in the EarMark™ system114, and placed around the cochlea of the living subject in anon-invasive fashion. Using the EarMark™ system with acommercially-available IGS system, submillimetric accuracy within thetemporal bone is demonstrated. In one embodiment, for over 234 targetregistrations, mean target registration error (TRE) was 0.76 mm with astandard deviation of 0.23 mm. The LADS and the fiducial frame may becustomized for a specific patient.

Furthermore, the system 100 includes an image acquisition device (notshown), such as a CT (computed tomography) imaging scanner or a MR(magnetic resonance) imaging scanner, for pre-operatively acquiring animage volume, i.e., a three-dimensional (hereinafter “3D”) radiographicimage, which contains the fiducial markers from the ear portion of thepatient. In one embodiment, the image volume, such a CT image, isacquired using clinically applicable, temporal-bone algorithms with scanthickness of about 0.5 mm.

Moreover, the system 100 includes a surgical instrument 120 having adistal end portion 122 for opening an access to the cochlea of thepatient. The surgical instrument 120 can be a high-speed surgical drillor a surgical scalpel. For a surgical drill, the distal end portion iscorresponding to the tip of the drill. For a surgical scalpel, thedistal end portion is corresponding to the cutting portion of thesurgical scalpel. Other types of surgical instruments can also be usedto practice the present invention. The surgical instrument can beoperated by a surgeon or at least partially by a man-made device such asa robot.

Additionally, the system 100 has an infrared tracking system forpre-operatively measuring a location of each fiducial marker andintra-operatively monitoring a location of the distal end portion of thesurgical instrument in the anatomic space of the patient. In theembodiment, the infrared tracking system includes a first opticalemitter 132 attached to the surgical instrument 120 as shown in FIGS.2A-2C, a second optical emitter 134 attached to the LADS 112 as shown inFIGS. 1B, 2A and 2B, respectively. The infrared tracking system 130 alsoincludes an optical tracker 130 having a position sensor 136, and aprocessor 138. Each of the first and second optical emitter 132 and 134can be an infrared emitter adapted for emitting infrared light and iscommunicable to the processor 138 through coupling means such as cable.The optical tracker 130 is adapted for receiving optical signals emittedfrom the first and second optical emitter 132 and 134 so as to detectthe position of each of the first and second optical emitter 132 and134. In one embodiment, a commercially available infrared trackingsystem (Polaris®, Northern Digital Inc., Waterloo, Canada) is employedto measure the location of each fiducial marker and the location of thedistal end portion of the surgical instrument in the anatomic space ofthe patient. Other tracking systems can also be used to practice thepresent invention.

The system 100 also includes a controller 140 adapted for, among otherthings, receiving and processing data related to the pre-operativelyacquired image volume, the pre-operatively measured location of eachfiducial marker and the intra-operatively monitored location of thedistal end portion of the surgical instrument so as to guide thesurgical instrument 120 along a predetermined path to open an access tothe cochlea of the patient. The controller 140 is programmed to performthe steps of identifying a centroid of each fiducial marker in thepre-operatively acquired image volume, registering the identifiedcentroid of each fiducial marker in the pre-operatively acquired imagevolume to the pre-operatively measured location of the correspondingfiducial marker in the anatomic space so as to determine a registrationtransformation, and mapping the intra-operatively monitored location ofthe distal end portion of the surgical instrument in the anatomic spaceonto a corresponding location in the pre-operatively acquired imagevolume by an inverse of the registration transformation, therebyintra-operatively displaying the location of the distal end portion ofthe surgical instrument. Furthermore, the controller 150 can beprogrammed to perform the step of disabling the surgical instrument whenthe surgical instrument departs from the predetermined path through adisabling device (not shown) associated with the surgical instrument.

As shown in FIG. 2A, the system 100 has an image displaying device 150,such as a monitor, in communication with the controller 140 forintra-operatively displaying the location of the distal end portion ofthe surgical instrument in the pre-operatively acquired image volume.

Referring now to FIG. 7, a method for providing an access to the cochleaof a living subject for performing a medical procedure is shownaccording to one embodiment of the present invention. The methodincludes the following steps: at step 710, a plurality of fiducialmarkers are non-invasively placed around the ear portion of the patient.In one embodiment, it is implemented by mounting an LADS with anattached fiducial frame onto a maxilla of the patient, where thefiducial frame contains the plurality of fiducial markers, as discussedabove, an EarMark™ system can be employed for non-invasively placing thefiducial markers around the ear portion of the patient. At step 720, oneor more image volumes are acquired pre-operatively from the ear portionof the living subject wearing the LADS and fiducial frame, where thepre-operatively acquired image volumes contain the image of the fiducialmarkers. The fiducial frame is removed from and reattached to the LADSbetween two CT imaging scans. Multiple CT imaging scans are necessary indetermining fiducial registration error (hereinafter “FRE”) of the imagespace, which is employed to determine TRE. These FREs are averaged usingsum of squares to determine an average FRE. At step 730, a centroid ofeach fiducial marker is identified from the pre-operatively acquiredimage volumes. In one embodiment, the image volumes (3D CT images) arereconstructed from the CT imaging scans by utilizing a high-performancecomputer. On these reconstructed image volumes, voxels (i.e., a surgicalsite) that lie within the ear portion of the living subject are selectedby the surgeon. In other words, a surgical excavation, i.e., amastoidectomy, is pre-operatively planned based on the radiographicimages.

After pre-operatively acquiring image volumes of the patient, the LADSand the fiducial frame are removed and saved for the patient. In the OR,after performing a general anesthesia, the living subject is re-fittedwith his/her customized LADS and the fiducial frame. A location of eachfiducial marker in an anatomic space of the ear portion of the livingsubject is measured using an infrared optical tracking system, such asPolaris®, at step 740. The identified centroid of each fiducial markerin the pre-operatively acquired image volume is registered to thepre-operatively measured location of the corresponding fiducial markerin the anatomic space at step 750. The image registration determines aregistration transformation and is performed by a computer/controller inconjunction with the infrared optical tracking system and customizedsoftware such as Voyger® (Z-Kat Inc., Hollywood, Fla.). The registrationtransformation, in one embodiment, includes a rigid-body transformation.

At step 760, a surgical instrument such as a surgical drill or surgicalscalpel is operated along a predetermined path to open an access to thecochlea of the patient. The surgical instrument has a distal endportion. The distal end portion of the surgical instrument isintra-operatively tracked/monitored in the anatomic space of the earportion of the living subject at step 770. The anatomic space of the earportion of the living subject is corresponding to the OR. Theintra-operatively monitored location of the distal end portion of thesurgical instrument in the anatomic space is mapped onto a correspondinglocation in the pre-operatively acquired image volume by an inverse ofthe registration transformation. The monitoring of the location of thedistal end portion of the surgical instrument is performed by theinfrared optical tracking system. The infrared optical tracking systemhas a first infrared emitter attachable to the surgical instrument, asecond infrared emitter attachable to the LADS mounted to the skull ofthe living subject, and an optical tracker adapted for receiving opticalsignals from the first optical emitter and the second optical emitter.The mapping step in one embodiment is performed with the computer. Atstep 780, the surgical instrument is intra-operatively guided throughvisualizing the location of the distal end portion of the surgicalinstrument in the pre-operatively acquired image volume. Furthermore,the skull of the living subject, or at least a portion of it, isintra-operatively tracked through the infrared optical tracking systemby the second infrared emitter attached to the LADS that is mounted tothe skull. Additionally, when the surgical instrument departs from thepredetermined path, a controller, such as a computer coupled with thesurgical instrument, generates a signal to disable the surgicalinstrument. Software codes and electric circuits for controlling thesurgical instrument in the present invention are custom-designed.

According to the present invention, an accurate access to the middle earvia the facial recess without violating the canal of the facial nerve,the horizontal semicircular canal, or the external auditory canal isachieved by utilizing a non-invasively fiducial system in conjunctionwith a tracked otologic drill, thereby making percutaneous cochlearimplantation technically feasible and doable. Because of the minimallyinvasive nature of the procedure, the surgery time is reduceddramatically, and the patient may not suffer from post-operativeswelling. Furthermore, at time of surgery, a cochlear implant device canbe activated and the patient may be asked if the device sounds better inthe position, or after advancing it in a little further, or in adifferent position.

Without intent to limit the scope of the invention, further exemplarymethods and their related results according to the embodiments of thepresent invention are given below.

EXAMPLES OF THE INVENTION

In the exemplary experiment provided herein it was proved that, giventhe systems accuracy, the middle ear may be safely accessed via thefacial recess using a single drill hole from the lateral aspect of themastoid cortex. The clinical correlation of this may be a percutaneouscochlear implant or other medical devices.

To facilitate an image-guided otologic surgery according to the presentinvention, a fiducial frame, an EarMark™ system developed by theinventors [9-11], is adapted for placing a plurality of fiducial markersin close proximity to the temporal bone of a patient in a non-invasivefashion, as shown in FIG. 1A. The EarMark™ system 114 is secured to askull 119 of the patient by mounting the LADS 112 onto the maxilla ofthe patient. The use of the EarMark™ system in conjunction with acommercially-available IGS system enables submillimetric accuracy withinthe temporal bone to be achieved. For example, with this system, forover 234 target registrations, TRE was 0.76 mm with a standard deviationof 0.23 mm. Additionally, two human skulls: Skull No. 1 and Skull No. 2,were employed to practice the present invention. Other fiducial framescan also be used to practice the invention.

As shown in FIGS. 1 and 2, a human skull 119 (Skull No. 1 or Skull No.2) was fitted with a dental bite block—the LADS 112 [12, 13] and placedon a surgical platform 190 in an operation room (OR) that iscorresponding to the anatomic space of the patient. Affixed to the LADS112 was the EarMark™ fiducial system 114 with fiducial markers 115placed around the temporal bone as shown in FIG. 1A. This unit thatincludes the skull 119, LADS 112 and EarMark™ 114 was then scanned by aCT imaging scanner using clinically-applicable, temporal bone algorithmswith a slice thickness=0.5 mm. The CT scanned data as well as the skull119 were transported to a laboratory, where the CT scanned data wasloaded onto commercially available software, such as Voyager®, foraccurate identification of the centroids of the fiducial markers [14].

As shown in FIG. 2, the image-guided otologic surgery setup 100 has aninfrared tracking system 130 with optical triangulation, such as acommercially-available Polaris® infrared tracking system, whichcommunicates with image analysis and visualization software, forexample, Voyager®, running on a personal computer 140. To allownavigation during the operative intervention, the operative or surgicalinstrument, an otologic drill 120, was fitted with an infrared emitter132. This drill 120 was registered to the system 100 so that the tip 122of the drill 120 was tracked in real time on a video monitor 150. Theskull 119 was also fitted with an infrared emitter 134.

Using the drill 120 as a localizing probe, the positions of the fiducialmarkers 115 on the EarMark™ system 114 were determined. Rigidregistration between physical space (the OR) and radiographic space (theCT scanned image) was performed using the fiducial markers 115 on theEarMark™ system 114. Using the algorithm described [13], a rigidtranformation was calculated by minimizing the differences in positionof the fiducial markers as identified on the CT scanned image with thoseidentified in the OR. This transformation was then applied to all datapoints in the CT scanned image in mapping the CT scanned image to thephysical space that the skull 119 was occupied in the OR. The IGSnavigation was thus enabled with the drill 120 serving as a localizerand the video monitor 150 showing the corresponding position in thepre-operative CT scanned image which was actively updated in axial,coronal, and saggital views.

After registration was complete, the EarMark™ system 114 was removedfrom the LADS 112, and the infrared emitter 134 was then attached to theLADS 112, which allowed unimpeded surgical access to the temporal bone,as shown in FIG. 2B. As both the drill 120 and skull 119 were beingactively tracked, each could be moved independently of the other whilecontinuously tracking, as shown in FIG. 2B.

Using this IGS system and tracked otologic drill fitted with a 2 mmcutting bit, a percutaneous approach to the middle ear via the facialrecess was undertaken. The drill was advanced by watching the videomonitors which actively updated its position in the CT scanned image.Care was taken to avoid vital structures—the canal of the facial nerve,the horizontal semicircular canal, and the external auditory canal. Withentry into the middle ear the drill bit could be seen via the externalauditory canal. Next, the mastoid was drilled in a conventional fashionpreserving the tunnel through which the percutaneous drill pass had beenmade. Photo documentation was performed to confirm that the track of thedrill was corresponding to that shown in the CT scanned image.

FIG. 3 demonstrated a composite of the experimental procedure. Panel (D)showed the skull 119 affixed with the infrared emitter 134 having theminimally-invasive, image-guided surgical procedure being performed. Thedrill 120 was tracked by the infrared emitter 132 while the skull 119was tracked by the infrared emitter 134 during operation. Thisconfiguration allowed movement of either the skull 119 and/or the drill120 independent of each other. Panels (A)-(C) showed respectively atransverse, coronal and sagittal view of the surgical site visualized inthe video monitor, monitoring the current position 122 of the tip end ofthe drill 120 that was registered to the CT scanned image. The position122 of the tip end of the drill 120 was identified by the crosshairs inthese panels (A)-(C). For each set-up, fiducial registration error wascalculated to be less than 0.8 mm and TRE was calculated to be less than0.7 mm. FIG. 4 showed an additional, optional view—an oblique magnifiedview with tracking of the drill. A wide line showed the path of thedrill as it approached the basal turn of the cochlea. The stylomastoidforamen was visible just below the path showing the distal,anterior-inferior course of the facial nerve.

FIGS. 5A and 5B were photographic images of Skull No. 1 taken afterminimally-invasive, image-guided, facial-recess approach to the middleear according to the present invention. For the sake of illustration, awire 510 extended down the drilled tunnel 520, as shown in FIG. 5A. Aview down the drilled tunnel 520 into the middle ear was shown in FIG.5B. FIGS. 5C and 5D were photographic images of Skull No. 1 taken aftertraditional mastoidectomy with preservation of the drill path. Asillustrated in FIGS. 5C and 5D, the vertical wire 512 was placed in thestylomastoid foramen and the horizontal wire 514 was placed through thetunnel. When turned anteriorly, as shown in FIG. 5D, the tunnel wasnoted to cross anterior to the facial nerve within the confines of thefacial recess.

FIG. 6 showed photographic images of Skull No. 2, where the image afterthe minimally-invasive, image-guided, facial-recess approach to themiddle ear with a wire 610 passing through the drilled tunnel 620 wasshown in FIG. 6A, while FIG. 6B showed the result after mastoidectomywith exposure of vital structures. The vertical wire 612 is located inthe facial canal, the arched wires 614 are in the semicircular canals,and bone over the central portion of the sigmoid sinus has been removed.Same as Skull No. 1, no vital structures were mechanically damaged bythe image-guided drilling according to the present invention.

In sum, the present invention, among other things, discloses a methodand system that utilize the non-invasively fiducial system with IGSsystems to achieve the submillimetric accuracy for image-guidedotologic/neurotologic surgery. Using this system in conjunction with atracked otologic drill, the middle ear was approached via the facialrecess using a single drill hole from the lateral aspect of the mastoidcortex. The path of the drill was verified by subsequently performing atraditional temporal bone dissection preserving the tunnel of bonethrough which the drill pass had been made.

The present invention thus provides an accurate approach to the middleear via the facial recess without violating the canal of the facialnerve, the horizontal semicircular canal, or the external auditorycanal. The exemplary results suggest that medical procedures such aspercutaneous cochlear implantation are technically feasible. Cochlearimplantation via mastoidectomy with extended facial recess is associatedwith a low incidence of complications and a high incidence of success[16, 17]. Because of the minimally invasive nature of the procedurewithout post-operative swelling, the cochlear implant device could beactivated at time of surgery and the patient could go home hearingshortly after the surgery, which is a dramatic difference from theconvertional system where patients waits 2-3 weeks to be activated.

The present invention also provides an additional layer of safety forotologic/neurotologic procedures. The active tracking of an otologicdrill allows triggering of alarms or other safety mechanisms should asurgical border be approached or a predetermined surgical path bedeparted. One of mechanisms according to the present invention isshutting off the surgical drill to prevent damage to collateral tissue[18]. Analogous to the facial nerve monitor, such safety systems mayallow more aggressive dissections while minimizing damage to vitalstructures.

Additionally, image-guided otologic surgery according to the presentinvention may prompt reworking of the current paradigm of wide surgicalexposure for otologic/neurotologic procedures. Approaches to the petrousapex may be accomplished under minimally-invasive conditions.Retrofacial approach to the sinus tympani may be feasible during routinechronic middle ear surgery. This new paradigm may also includeintegration of other exciting technologies such as robotic surgery inthe form of robotic mastoidectomy.

The foregoing description of the exemplary embodiments of the inventionhas been presented only for the purposes of illustration and descriptionand is not intended to be exhaustive or to limit the invention to theprecise forms disclosed. Many modifications and variations are possiblein light of the above teaching.

The embodiments were chosen and described in order to explain theprinciples of the invention and their practical application so as toenable others skilled in the art to utilize the invention and variousembodiments and with various modifications as are suited to theparticular use contemplated. Alternative embodiments will becomeapparent to those skilled in the art to which the present inventionpertains without departing from its spirit and scope. Accordingly, thescope of the present invention is defined by the appended claims ratherthan the foregoing description and the exemplary embodiments describedtherein.

REFERENCES

-   [1]. Roberts D W, Strohbehn J W, Hatch et al. A frameless sterotaxic    integration of computerized tomographic graphic imaging and the    operating microscope. J Neurosurg 1986; 65:45-49.-   [2]. Weinberg J S, Lang F F, and Sawaya R. Surgical management of    brain metastases. Curr Oncol Rep 2001, 3(6):476-83.-   [3]. Wisoff J H, Boyett J M, Berger M S, Brant C, LI H, Yates A J,    McGuire-Cullern P, Turski P A, Sutton L N, Allen J C, Packer R J,    and Finlay J L. Current neurosurgical management and the impact of    the extent of resection in the treatment of malignant gliomas of    childhood: a report of the Children's Cancer Group trial no.    CCG-945. J of Neurosurgery 1998, 89(1):52-9.-   [4]. Sargent E W and Bucholz R D. Middle cranial fossa surgery with    image-guided instrumentation. Otolaryngol Head Neck Surg 1997;    117:131-4.-   [5]. Raine C H, Strachan D, and Gopichandran T. How we do it: Using    a surgical navigation system in the management of the ossified    cochlea. Cochlear Implants International 2003; 4:96-101.-   [6]. Caversaccio M, Romualdez J, Vaecgker Rm et al. Valuable use of    computer-aided surgery in congenital bony aural atresia. J Laryngol    Otol 2003; 117:241-8.-   [7]. Raabe A, Krishnan R, Wolff R, Hermann E, Zimmermann M,    Seifert V. Laser surface scanning for patient registration in    intracranial image-guided surgery. Nuerosurgery 2002; 50:797-803.-   [8]. Schlaier J, Warnat J, Brawanski A. Registration accuracy and    practicability of laser-directed surface matching. Comput Aided Surg    2002; 7:284-290.-   [9]. Labadie R F, Shah R J, Harris S S, Cetinkaya E, Haynes D S,    Fenlon M, Juscyzk S, Galloway R L, Fitzpatrick J M. Image—Guided    Otologic Surgery: Submillimeter Accuracy within the Temporal Bone.    Otolaryngology-Head and Neck Surgery (in submission). Presented at    the 2003 Annual Meeting of the American Academy of Otolaryngology    Head and Neck Surgery, Orlando, Fla., September 21-24.-   [10]. Labadie R F, Fenlon M, Devikalp H, et al. Image-guided    otologic surgery. Computer Assisted Radiology and Congress and    Exhibition (eds: Lemke H U, Vannier M W, Inamura K, Farman A G, Doi    K, Reiber J H C) pp. 627-32. Elsevier Science, Amsterdam, The    Netherlands, 2003.-   [11]. Labadie R F, Shah R J, Harris S S, Cetinkaya E, Haynes D S,    Fenlon M, Juscyzk S, Galloway R L, Fitzpatrick J M. Submillimetric    Target-Registration Error using a Novel, Non-Invasive Fiducial    System (the EarMark™) for Image Guided Otologic Surgery. Comp Aided    Surg (in submission). Presented at the 17th International Congress    and Exhibition of Computer Assisted Radiology and Surgery, London,    England, June 25-28.-   [12]. Fenlon M R, Jusczyzck A S, Edwards P J, and King A P. Locking    acrylic resin dental stent for image guided surgery. J of Prosthet    Dent 2000; 83:482-5.-   [13]. Edwards P J, King A P, Maurer C R, et al. Design and    evaluation of a system for microscope-assisted guided interventions    (MAGI). IEEE Trans Med Imag 2000; 19:1082-1093.-   [14]. ang M Y, Maurer Jr. C R, Fitzpatrick J M, and Maciunas R J. An    automatic technique for finding and localizing externally attached    markers in CT and MR volume images of the head. IEEE Trans Biomed    Eng 1996; 43:627-37.-   [15]. Fitzpatrick J M, West J M, Maurer Jr. C R. Predicting error in    rigid-body, point-based registration. IEEE Trans Med Imaging 17,    694-702, 1998.-   [16]. Cohen N L, Hoffman R A, Stroschein M. Medical or surgical    complication related to the nucleus multichannel cochlear implant.    Ann Otol Rhinol Laryngol 1988; 97:8-13.-   [17]. Kronenberg J, Baumgartner W, Migirov L, et al. The suprameatal    approach: an alternative surgical approach to cochlear implantation.    Otol Neurotol 2004; 25:41-45.-   [18]. Labadie R F and Fitzpatrick J M, Surgical Instrument    Disablement Via Image-Guided Position Feedback, Patent Pending    (filed Mar. 22, 2004).

What is claimed is: 1.-15. (canceled)
 16. A system for providing anaccess o a cochlea of a living subject, comprising: a. means fornon-invasively placing a plurality of fiducial markers surrounding thecochlea of the living subject; b. an imaging acquisition device forpre-operatively acquiring an image volume from the cochlea of the livingsubject, the pre-operatively acquired image volume containing the imageof the plurality of fiducial markers; c. a surgical instrument having adistal end portion for opening an access to the cochlea of the livingsubject; d. an infrared tracking system for pre-operatively measuring alocation of each fiducial marker and intra-operatively monitoring alocation of the distal end portion of the surgical instrument in theanatomic space of the cochlea of the living subject; e. a controller forreceiving and processing data related to the pre-operatively acquiredimage volume, the pre-operatively measured location of each fiducialmarker and the intra operatively monitored location of the distal endportion of the surgical instrument so as to guide the surgicalinstrument along a predetermined path to open an access to the cochleaof the living subject; and f. an image display device in communicationwith the controller for displaying the location of the distal endportion of the surgical instrument.
 17. The system of claim 16, whereinthe placing means comprises: a. a locking dental acrylic resin splint(LADS) mountable to a maxilla of the living subject, wherein the LADSincludes a central portion with an extension at a predeterminedposition, and two lateral portions attached to the central portion; andb. a fiducial frame attachable to the LADS by the extension forreceiving the plurality of fiducial markers.
 18. The system of claim 17,wherein the infrared tracking system comprises a first optical emitterattachable to the surgical instrument, and a second optical emitterattachable to the LADS, and an optical tracker adapted for receivingoptical signals from the first optical emitter and the second opticalemitter.
 19. The system of claim 18, wherein each of the first andsecond optical emitters comprises an infrared emitter.
 20. The system ofclaim 16, wherein the imaging acquisition device comprises a CT scanningdevice.
 21. The system of claim 16, wherein the surgical instrumentcomprises a drill, and the distal end portion of the surgical instrumentcomprises the tip of the drill.
 22. The system of claim 16, wherein thesurgical instrument comprises a surgical scalpel, and the distal endportion of the surgical instrument comprises the cutting portion of thesurgical scalpel.
 23. The system of claim 16, wherein the controller isprogrammed to perform the steps of: a. identifying a centroid of eachfiducial marker in the pre-operatively acquired image volume; b.registering the identified centroid of each fiducial marker in thepre-operatively acquired image volume to the pre-operatively measuredlocation of the corresponding fiducial marker in the anatomic space soas to determine a registration transformation; and c. mapping theintra-operatively monitored location of the distal end portion of thesurgical instrument in the anatomic space onto a corresponding locationin the pre-operatively acquired image volume by an inverse of theregistration transformation, thereby intra-operatively displaying thelocation of the distal end portion of the surgical instrument throughthe image displaying device.
 24. The system of claim 23, the controlleris further programmed to perform the step of disabling the surgicalinstrument when the surgical instrument departs from the predeterminedpath.
 25. The system of claim 16, wherein the image displaying devicecomprises a monitor.
 26. The system of claim 16, wherein the access tothe cochlea of the living subject is a single passage from the lateraledge of the skull to the cochlea. 27.-38. (canceled)
 39. A system forproviding an access to a cochlea of a living subject for performing amedical procedure, comprising: a. a platform; b. means forpre-operatively determining a location for positioning the platformproximate to the cochlea of the living subject; c. means for positioningthe platform proximate to the pre-operatively determined location; d. asurgical instrument guide for guiding a surgical instrument towards aregion of interest of the living subject, wherein the surgicalinstrument has a distal end portion in operation reaching the region ofinterest first, for opening an access to the cochlea of the livingsubject; and e. means for intra-operatively monitoring at least alocation of the distal end portion of the surgical instrument so thatthe surgical instrument is operated substantially along a predeterminedpath.
 40. The system of claim 39, wherein the access to the cochlea ofthe living subject is a single passage from the lateral edge of theskull to the cochlea.
 41. The system of claim 39, further comprisingmeans for performing a medical procedure through the access.
 42. Thesystem of claim 41, wherein the means for performing a medical procedurecomprises one of a cochlea implant, a drug delivery system, a carrierdevice, a medical detecting system, a medical treatment system, and anycombination of them.
 43. The system of claim 39, wherein the platformcomprises a fiducial frame with at least one fiducial marker.
 44. Thesystem of claim 43, wherein the fiducial frame comprises a customizedfiducial frame.
 45. The system of claim 39, further comprising means foroperating the surgical instrument.
 46. The system of claim 45, whereinthe operating means comprises a man-made device.
 47. The system of claim39, wherein the surgical instrument guide comprises an infrared trackingsystem.
 48. The system of claim 39, wherein the surgical instrumentcomprises a drill, and the distal end portion of the surgical instrumentcomprises the tip of the drill.
 49. The system of claim 39, wherein thesurgical instrument comprises a surgical scalpel, and the distal endportion of the surgical instrument comprises the cutting portion of thesurgical scalpel.
 50. The system of claim 39, wherein thepre-operatively determining means comprises a controller and/or softwarestored on a computer readable medium for causing the controller toperform at least a registration procedure.
 51. The system of claim 39,wherein the intra-operatively monitoring means comprises a controllerand/or software stored on a computer readable medium for causing thecontroller to perform at least an image-guided procedure.
 52. The systemof claim 51, wherein the intra-operatively monitoring means furthercomprises an image displaying device in communication with thecontroller.
 53. The system of claim 39, further comprising means fordisabling the surgical instrument when the surgical instrument departsfrom the predetermined path. 54.-56. (canceled)